Formation of [K(18-crown-6)]2Bi2 and the influence of 18-crown-6 on the crystallization of bismuth-based Zintl clusters obtained from Bi22−

Abstract

So far, homoatomic polybismuthide Zintl anions, which can be used as starting materials for larger binary or ternary, bismuth-based clusters, have always been isolated from potassium-based Zintl phases using 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane (crypt-222) to sequester the K+ counterions. The formation of larger clusters from such anions is still poorly understood, and a change of the sequestering agent might lead to the crystallization of missing links in the cluster formation pathways, which is why – in addition to cost considerations – such variants are being investigated. Herein, we present the synthesis and characterization of the first homoatomic polybismuthide salt with a 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6) complex as counterion, [K(18-crown-6)]2Bi2 (1). By means of mass spectrometry, we show that compound 1 behaves, generally, alike [K(crypt-222)]2Bi2 in reactions with [CpRu(NCMe)3]+, forming the previously reported cluster anion [{CpRu}3Bi6]−. However, crystallization of this cluster can only be achieved in the presence of [PF6]− anions, yielding [{K(18-crown-6)}2{PF6}][{CpRu}3Bi6] ⋅ en (2). This shows that [K(18-crown-6)]+, if paired up with an additive like [PF6]−, indeed is a (cheaper) alternative for the crystallization of anionic bismuth-based clusters.